Balsa blankets and/or parts cut out of balsa blankets are laminated to a great extent into shell structures of fibre-reinforced plastics, e.g. epoxy and fibre glass, due to their high compressive strength and rigidity in relation to weight. Balsa blankets are used in great amounts in large shell structures, such as boat hulls or fibre-glass blades. Balsa blankets are sold in standard sizes, e.g. about 0.6 m×1.2 m, from which the parts needed for the shell structure are cut. This cutting process results in a relatively large waste of material, especially when cutting out non-rectangular parts. An example of balsa blankets is the balsa blanket BALTEK®SB, Structural End-Graen Balsa from Alkan Composites Ltd.